Method and apparatus for determining and communicating multi-stage sidelink control information

ABSTRACT

First stage SCI can be determined. The first stage SCI including information can indicate whether or not a second stage SCI is being transmitted. The first stage SCI can be periodically transmitted. The second stage SCI can be determined. The second stage SCI can be transmitted.

BACKGROUND 1. Field

The present disclosure is directed to a method and apparatus forcommunicating two stage Sidelink Control Information (SCI).

2. Introduction

Presently, wireless communication devices, such as User Equipment (UE),communicate with other communication devices using wireless signals.Control channel structure and procedure enhancement can be used in NewRadio (NR) Vehicle to Everything (V2x) to support different SCI formatsand different aggregation levels and still maintain the same decodingcomplexity as that of Long Term Evolution (LTE) V2x. In LTEVehicle-to-everything (V2x), Physical Sidelink Control Channel (PSCCH)is defined to carry a Scheduling Assignment (SA), which is required byUE to properly detect and decode the corresponding Physical SidelinkShared Channel (PSSCH). For example, Sidelink Control Information (SCI)is transmitted over the PSCCH, which carries the information related tothe transmission of data over the PSSCH.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which advantages and features of thedisclosure can be obtained, a description of the disclosure is renderedby reference to specific embodiments thereof which are illustrated inthe appended drawings. These drawings depict only example embodiments ofthe disclosure and are not therefore to be considered to be limiting ofits scope. The drawings may have been simplified for clarity and are notnecessarily drawn to scale.

FIG. 1 is an example block diagram of a system according to a possibleembodiment;

FIG. 2 is an example component illustration of two stage SCI accordingto a possible embodiment;

FIG. 3 is an example illustration of sidelink Radio Resource Control(RRC) configuration according to a possible embodiment;

FIG. 4 is an example illustration of two stage SCI with scheduling inthe same Transmit Time Interval (TTI) according to a possibleembodiment;

FIG. 5 is an example illustration of two stage SCI with scheduling indifferent Bandwidth Parts (BWPs) according to a possible embodiment;

FIG. 6 is an example illustration of two stage SCI with scheduling indifferent numerology according to a possible embodiment;

FIG. 7 is an example illustration of two stage SCI where the first stageindicates the presence or absence of the second stage according to apossible embodiment;

FIG. 8 is an example illustration of a transmitting UE in the firststage specifying the modification periodicity of the second stage SCIaccording to a possible embodiment;

FIG. 9 is an example illustration of a receiving UE explicitlyrequesting a transmitting UE to send the second stage SCI according to apossible embodiment;

FIG. 10 is an example illustration of a UE joining a group usinggroupcast transmission according to a possible embodiment;

FIG. 11 is an example illustration of a new UE announcing itself to agroup according to a possible embodiment;

FIG. 12 is an example illustration of discovery and second stage SCItransmission for a group according to a possible embodiment;

FIG. 13 is an example illustration of group specific signaling accordingto a possible embodiment;

FIG. 14 is an example flowchart outlining the operation of a wirelesscommunication device according to a possible embodiment;

FIG. 15 is an example flowchart outlining operation of a wirelesscommunication device according to a possible embodiment; and

FIG. 16 is an example block diagram of an apparatus according to apossible embodiment.

DETAILED DESCRIPTION

According to a possible embodiment, first stage SCI can be determined.The first stage SCI including information can indicate whether or not asecond stage SCI is being transmitted. The first stage SCI can beperiodically transmitted. The second stage SCI can be determined. Thesecond stage SCI can be transmitted. At least some embodiments canprovide a procedure for multi-stage SCI design for NR V2x. At least someembodiments can provide information on scheduling enhancement formulti-stage SCI for Unicast (UC) and Groupcast (GC) transmission.

FIG. 1 is an example block diagram of a system 100 according to apossible embodiment. The system 100 can include a UE 110, at least onenetwork entity 120 and 125, and a network 130. The UE 110 can be awireless wide area network device, a user device, a wireless terminal, aportable wireless communication device, a smartphone, a cellulartelephone, a flip phone, a personal digital assistant, a smartwatch, apersonal computer, a tablet computer, a laptop computer, a selectivecall receiver, an Internet of Things (IoT) device, a vehicle, or anyother user device that is capable of sending and receiving communicationsignals on a wireless network. The at least one network entity 120 and125 can be a wireless wide area network base station, can be a NodeB,can be an enhanced NodeB (eNB), can be a New Radio (NR) NodeB (gNB),such as a Fifth Generation (5G) NodeB, can be an unlicensed network basestation, can be an access point, can be a base station controller, canbe a network controller, can be a Transmission/Reception Point (TRP),can be a different type of network entity from the other network entity,and/or can be any other network entity that can provide wireless accessbetween a UE and a network.

The network 130 can include any type of network that is capable ofsending and receiving wireless communication signals. For example, thenetwork 130 can include a wireless communication network, a cellulartelephone network, a Time Division Multiple Access (TDMA)-based network,a Code Division Multiple Access (CDMA)-based network, an OrthogonalFrequency Division Multiple Access (OFDMA)-based network, a Long TermEvolution (LTE) network, a NR network, a 3rd Generation PartnershipProject (3GPP)-based network, a 5G network, a satellite communicationsnetwork, a high altitude platform network, the Internet, and/or othercommunications networks.

In operation, the UE 110 can communicate with the network 130 via atleast one network entity 120. For example, the UE 110 can send andreceive control signals on a control channel and user data signals on adata channel.

The UE 110 can also communicate with other UEs (not shown) by using V2x.NR V2x can support UC, GC, and Broadcast (BC) types of traffic. Therecan be multiple SCI formats due to different transmission mode settingsfor UC, GC, and BC transmission, which can increase the UE blinddecoding complexity. Also, the data for UC or GC generally should onlybe known to the destination UEs or a destination group of UEs,respectively, and the data generally should be protected from anonymousUEs that are not part of the destination groups.

Due to the BC nature of the majority of V2x applications and also aspart of sensing procedure for selecting empty resources, all UEs canmonitor and decode PSCCH. Therefore, to keep the blind decodingcomplexity of the UE to a reasonable level, only one SCI format andfixed location of PSCCH within the allocated resources can be defined.

The content of SCI format 1, which can be used to schedule PSSCH, mainlydesigned for LTE V2x, is detailed in Table 1.

TABLE 1 Priority 3 bits Resource reservation 4 bits Frequency resourcelocation ┌log₂(N_(subchannel) ^(SL) (N_(subchannel) ^(SL) + 1)/2)┐ ofinitial transmission and retransmission Time gap between initial 4 bitstransmission and retransmission Modulation and coding 5 bits schemeRetransmission index 1 bit Transmission format 1 bit

In the current NR Release 16 (R16) V2x discussion, 2 stage SCI can beconsidered with the main motivation being to separate the sensingprocedure, which can be broadcasted to all UEs, with that of the grantrequired to decode for the UC & GC transmission. Second stage SCI canalso be protected with Cyclic Redundancy Check (CRC) masked by a Layer 1destination Identifier (ID) so that only the intended UE can decode theinformation. The second stage SCI can also be transmitted in the dataregion as part of PSSCH resource which can offload some control channelresources to the data region.

For PSCCH, a Layer-1 destination ID can be explicitly included in SCI. ALayer-1 source ID can also be included in SCI. A Hybrid Automatic RepeatRequest (HARQ) process ID can also be included in SCI. A New DataIndicator (NDI) can also be included in SCI. A Redundancy Version (RV)can also be included in SCI. Some of the above information may or maynot be present in some operations, such as depending on whether they areused for UC, GC, BC, and/or other operations.

Although motivation for proposing two stage SCI can be to reduce theblind decoding complexity during sensing and privacy for UC/GCtransmission, some scheduling optimization in the control channelresources can be considered, such as when to transmit the second stageSCI, whether the second stage SCI should be transmitted all the time,and/or whether it should be event driven for UC and GC transmissions.

In one possible operation, separation of the SCI into two parts can beused for GC or UC sidelink transmission. The SCI part 1 can be relatedto resource reservation and can be BC to all UEs. The SCI part 2 can beused for BC, UC, and/or GC. If SCI part 2 is related to UC or GC, it mayonly be known to the destination UEs. If the SCI part 2 has its CRCmasked by an ID associated with UC or GC sidelink, then it can be moreprotected.

One possible 2-stage PSCCH design can follow the principle of keepingthe first stage SCI as small as possible with fixed pre-defined searchspace. This can enable flexibility of NR V2x when different use casesand scenarios need to be considered in a distributed manner. The firststage SCI can point to the exact time and frequency resources and formatof the second stage SCI and indicate the SCI format. In contrast, thesecond stage SCI can be flexible in terms of time and frequencylocations as well as SCI formats.

In another possible operation, SCI can split into two parts, where SCIpart 1 can include the location of time-frequency resource used byPSSCH, resource reservation, priority and SCI part 2 can contain therest of SCI. SCI part 1 and SCI part 2 can be encoded separately. No CRCscrambling may be performed on SCI part 1 so that all UEs can decode SCIpart 1. SCI part 2 can be CRC scrambled by UE-specific Radio NetworkTemporary Identifier (RNTI) or group RNTI so that only the intended UEscan learn SCI part 2 and further decode PSSCH. SCI part 1 can be carriedby PSCCH and SCI part 2 can be piggybacked on PSSCH or the SCI part 2occupies the PSSCH resource.

In another possible operation, pre-emptive reservation and announcementmessages can be control messages without any data linked to it, but caninstead point to other control messages. In a possible operation for LTEUu interface two stage design, two stage PDCCH with DCI flag and DCIformat size indicator can be used.

In the present disclosure, the term eNB/gNB can be used for a basestation, but it can be replaceable by any other radio access node, suchas a Base Station (BS), an eNB, a gNB, an Access Point (AP), and otherradio access nodes. Furthermore, disclosed embodiments are describedmainly in the context of 5G NR. However, the embodiments are alsoequally applicable to other mobile communication systems supportingserving cells/carriers being configured for sidelink communication, suchas over a PC5 interface, or configured for other communications.

FIG. 2 is an example component illustration 200 of two stage SCIaccording to a possible embodiment. The illustration 200 can show thecommunication between a first transmitting UE 210 and a second receivingUE 220. At 230 and 250, the transmitting UE 210 can respectivelyconfigure and determine the SCI content of each stage, which can includeSCI format and/or SCI size of the second stage SCI, aggregation level ofthe second stage SCI, and/or the transmission periodicity of the secondstage SCI. The terms configure and determine can be consideredsynonymous. At 240, the transmitting UE 210 can transmit a fast controlchannel including the first stage SCI to the receiving UE 220. At 260,the transmitting UE 210 can transmit the slow control channel includingthe second stage SCI to the receiving UE 220. At 270, the receiving UEcan receive the control channels, other control information, and/ordata.

The configurations of the SCI can be addressed in different stages,where the content of the first stage can include the parameters that aredirectly or indirectly related to the sensing procedure and thefast-varying component of the SCI, which can mean a frequently changingparameter of the SCI. The word frequent can imply that these parameterscan be transmitted in all the time slots along with every scheduledsidelink data packet in a PSSCH, such as the minimum parameter set ofthe SCI that can be signaled each time a PSSCH is scheduled. The fastPSCCH can also be referred to in one or more ways as fast PSCCH, fastsidelink control information, and/or fast sidelink control channel.

First stage SCI content can be a fixed size to keep the blind decodingcomplexity low. For example, when the second stage is not beingtransmitted, an explicit indicator can inform its presence or absence,otherwise the Time/Frequency (T/F) resource of the second stage SCI bitscan be reserved or set to dummy values or an invalid Resource Block (RB)assignment, such as all ones set for all frequencies. In a possibleexample, when the second stage SCI is transmitted on a portion of theT/F resources of the PSSCH, such portion of the T/F resources can bereused for data transmission when the first stage SCI indicates theabsence of the presence of the second stage SCI or the modificationperiod timer has not expired.

In another possible embodiment, instead of an extra indicator to denotethe presence or absence of second stage SCI where the extra indicatorcan be one of the reserved bits in the first stage SCI field, an invalidvalue of any first stage SCI field(s) can be used to indicate theabsence of second stage SCI. For example, an invalid RB assignment forthe second stage control channel resource can imply the absence ofsecond stage SCI transmission.

In a method of a possible embodiment, the configuration of the firststage can also directly and indirectly addresses the configuration ofthe second stage in its SCI content. This configuration of the secondstage can include the one or more of the following parameters related tothe second stage: resource allocation of the second control channel,transmission periodicity, SCI format or SCI sizes, aggregation level,and/or other parameters.

FIG. 3 is an example illustration 300 of sidelink RRC configurationaccording to a possible embodiment. The illustration 300 can show NR Pc5RRC configuration, such as semi-static configuration of the second stageSCI between a first car 310, such as a transmitting UE, and a second car320, such as a receiving UE. This can further show Pc5 RRC connectionduring UC connection establishment. At least for the UC transmission,the configuration of the second stage SCI can be semi-staticallyconfigured, which can include the Control Resource Set (CORESET)configuration, transmission periodicity, SCI formats, SCI sizes,candidates, and other configuration, using a NR-Pc5 RRC message, L2sidelink Medium Access Control (MAC) Control Element (CE), and/or usingother message(s).

The configuration of the second stage can include the parameters thatare directly or indirectly slow varying components of the SCI andrelated to the data decoding of PSSCH. The parameters can includeModulation and Coding Scheme (MCS), Transmit Power Control (TPC)command, Sidelink-Channel State Information (S-CSI) request, CodebookBlock Group (CBG) transmission information, CBG flushing information,Demodulation Reference Signal (DMRS) Sequence Initialization, sourceidentifier, beam/Transmission Configuration Indicator (TCI) state,spatial relation for S-CSI, and/or other information.

The word slow can imply that these parameters need not be transmitted inall the time slots along with every scheduled sidelink data packet inPSSCH. For example, remaining parameter sets other than the minimumparameter set may be signaled less often than at every PSSCH schedulingoccasion.

FIG. 4 is an example illustration 400 of two stage SCI with schedulingin the same TTI according to a possible embodiment. The illustration 400can include TTIs 1-3, with TTIs 1 and 2 including fast PSCCH and slowPSCCH and TTIs 2 and 3 including fast PSCCH.

FIG. 5 is an example illustration 500 of two stage SCI with schedulingin different BWPs according to a possible embodiment. The illustration500 can include different carriers 1 and with different respective BWPs1 and 2, as well as TTIs 1-4. TTIs 1 and 4 can include fast PSCCH oncarrier 1 and BWP 1 and slow PSCCH on carrier 2 and BWP 2. TTIs 2 and 3can include fast PSCCH on carrier 1 and BWP 1.

FIG. 6 is an example illustration 600 of two stage SCI with schedulingin different numerology according to a possible embodiment. In theillustration 600, TTIs 1-4 on carrier 1 with BWP 1 and numerology 1 caninclude fast PSCCH and TTIs 1 and 4 on carrier 2 with BWP 2 andnumerology 2 can include slow PSCCH. As shown in the illustrations 400,500, and 600, the second stage SCI can be scheduled in the same BWP withthe same or next time slot as that of the first stage SCI or can bescheduled in different BWPs with the same or different numerology.

First stage SCI content can be a fixed size to keep the blind decodingcomplexity low. When the second stage is not being transmitted, anexplicit indicator can inform its presence or absence, otherwise the T/Fresource of the second stage SCI bits can be reserved or set to dummyvalue or invalid RB assignments, such as all ones or all frequencies. Ina possible example, when the second stage SCI is transmitted on aportion of the T/F resources of the PSSCH, such portion of the T/Fresources can be reused for data transmission when the first stage SCIindicates absence of the presence of the second stage SCI or themodification period timer has not expired.

According to another possible embodiment, the destination ID may allones to represent BC transmission.

FIG. 7 is an example illustration 700 of two stage SCI where the firststage indicates the presence of the second stage according to a possibleembodiment. The illustration 700 can show communication between atransmitting first UE 710 and multiple receiving UEs including a secondUE 712, a third UE 714, and a fourth UE 716. In a first transmissionprocess, at 720, the first UE 710 can transmit a first stage SCI BCcommunication. The first stage SCI can include T/F of PSSCH, NDI,destination ID, T/F of second stage SCI, an indicator of the presence orabsence of the second stage SCI, and/or other information. At 730, thefirst UE 720 can send a second stage SCI in a UC SCI transmission to thethird UE 714. The second stage SCI can include RV, HARQ process number,MCS, TPC command, S-CSI request, and/or other information. At 740, thefirst UE 710 can transmit UC data to the third UE 714. In a secondtransmission process, at 750, the first UE 710 can transmit a firststage SCI BC communication. The first stage SCI can include T/F ofPSSCH, NDI, destination ID, T/F of second stage SCI, an indicator of thepresence or absence of the second stage SCI, and/or other information.At 760, the first UE 710 can transmit UC data to the third UE 714.According to this embodiment, an indication can be provided in the firststage SCI that indicates when the second stage SCI is being transmitted.The indication can further be a flag bit that can be a 0 or 1 toindicate the presence or absence of second stage SCI.

FIG. 8 is an example illustration 800 of a transmitting UE in the firststage specifying the modification periodicity of the second stage SCIaccording to a possible embodiment. The illustration 800 can showcommunication between a transmitting first UE 810 and multiple receivingUEs including a second UE 812, a third UE 814, and a fourth UE 816. In afirst transmission process, at 820, the first UE 810 can transmit afirst stage SCI BC communication. The first stage SCI can include T/F ofPSSCH, NDI, destination ID, T/F of second stage SCI, a modificationperiodicity, and/or other information. At 825, the first UE 820 can senda second stage SCI in a UC SCI transmission to the third UE 814. Thesecond stage SCI can include RV, HARQ process number, MCS, TPC command,S-CSI request, and/or other information. At 830, the first UE 810 cantransmit UC data to the third UE 814. In a second transmission process,at 835, the first UE 810 can transmit a first stage SCI BCcommunication. The first stage SCI can include T/F of PSSCH, NDI,destination ID, T/F of second stage SCI, a modification periodicity,and/or other information. At 840, the first UE 810 can transmit UC datato the third UE 814. In an n^(th) transmission process, after themodification period expires, at 845, the first UE 810 can transmit afirst stage SCI BC communication. The first stage SCI can include T/F ofPSSCH, NDI, destination ID, T/F of second stage SCI, a modificationperiodicity, and/or other information. At 850, the first UE 820 can senda second stage SCI in a UC SCI transmission to the third UE 814. Thesecond stage SCI can include RV, HARQ process number, MCS, TPC command,S-CSI request, and/or other information. At 855, the first UE 810 cantransmit UC data to the third UE 814. According to this embodiment, amodification periodicity can be transmitted in the first stage SCI. Inanother related embodiment, the modification periodicity can be semistatically configured with L3 or L2 signaling options like NR Pc5 RRC orsidelink MAC CE as shown in the illustrations 300 and 800. A bit mapfield containing modification periodicity can include a time slot index,a periodicity, and/or other information.

Additionally, when a slow PSCCH, such as the second stage, is notpresent in a given time slot, a receiving UE can utilize the grant froma previously most recently received and/or decoded PSCCH. In otherwords, when the second stage SCI is not being transmitted, then the UEcan assume that the content of the second stage remains same until thenext modification period or until the next timer expiry.

FIG. 9 is an example illustration 900 of a receiving UE explicitlyrequesting a transmitting UE to send the second stage SCI according to apossible embodiment. The illustration 900 can show communication betweena transmitting first UE 910 and multiple receiving UEs including asecond UE 912, a third UE 914, and a fourth UE 916. In a firsttransmission process, at 920, the first UE 910 can transmit a firststage SCI BC communication. The first stage SCI can include T/F ofPSSCH, NDI, destination ID, T/F of second stage SCI, an indicator of thepresence or absence of the second stage SCI, and/or other information.At 925, the first UE 920 can send a second stage SCI in a UC SCItransmission to the third UE 914. The second stage SCI can include RV,HARQ process number, MCS, TPC command, S-CSI request, and/or otherinformation. At 930, the first UE 910 can transmit UC data to the thirdUE 914. In a second transmission process, at 935, the first UE 910 cantransmit a first stage SCI BC communication. The first stage SCI caninclude T/F of PSSCH, NDI, destination ID, T/F of second stage SCI, anindicator of the presence or absence of the second stage SCI, and/orother information. At 940, the first UE 910 can transmit UC data to thethird UE 914. In a third transmission process, at 945, the first UE 910can transmit a first stage SCI BC communication. The first stage SCI caninclude T/F of PSSCH, NDI, destination ID, T/F of second stage SCI, anindicator of the presence or absence of the second stage SCI, and/orother information. At 950, the first UE 910 can transmit UC data to thethird UE 914. At 955, the third UE 914 can send Sidelink FeedbackControl Information (SFCI)/Physical Sidelink Feedback Channel (PSFCH)including an explicit indication to transmit the second stage SCI. Forexample, the receiving third UE 914 can explicitly ask the transmittingUE 910 in Layer 1 (L1) or Layer 2 (L2) signaling, such as in L1 SFCI,such as via a PSFCH, or in a SL MAC CE, to transmit the second stagewith updated scheduling information in the second stage.

According to another possible embodiment, based on the received CSI froma receiving UE, a transmitting UE can update the scheduling information,such as MCS, precoder, beam/TCI-state, and other information, andtransmit the second stage with an updated scheduling information in thesecond stage SCI. According to another possible embodiment, themodification period timer can be (re)-started when the receiving UEreceives an indication of the second stage SCI. The indication of thepresence of the second stage SCI can be sent in the first stage SCI orimplicitly assumed based on the valid/invalid RB assignment fieldindicated in the first stage SCI.

According to another possible embodiment, the receiving UE may not beexpected to decode the Transport Block (TB) of PSSCH if the first stageSCI indicates the presence of second stage SCI, but the UE fails todecode the second stage SCI. In this case, the UE may not be expected todecode the transport TB of PSSCH and can send a NACK on a commonfeedback resource or explicit feedback indicator on a dedicated feedbackresource in SFCI, such as on a feedback channel, to request thetransmission of second stage SCI again. The UE also may not be expectedto apply previously decoded configuration of second stage SCI to decodethe TB of PSSCH. Applying wrong second stage SCI for data decoding canresult in soft buffer corruption. Hence, to avoid the soft buffercorruption, the UE procedure can include to not decode the PSSCH for adata packet where the receiving UE fails to decode second stage SCI.

According to another possible embodiment, the second stage SCI may bepresent even if the first stage SCI indicates absence of the presence ofthe second stage SCI or the modification period timer has not expired.This may be for the case of BC or GC transmission. A UE may not beexpected to decode the second stage SCI for a TB if the first stage SCIindicates absence of the presence of the second stage SCI or themodification period timer has not expired, and the UE has previouslyreceived the second stage SCI for the same TB, such as at the start ofthe modification period or when a new TB is scheduled.

If the first stage SCI indicates absence of the second stage SCI or themodification period timer has not expired, the receiving UE can assumethat the current PSSCH transmission is a retransmission of a TBcorresponding to the most recently received second stage SCI. Theretransmission may be with the same MCS and RV as that indicated in thesecond stage SCI. In one example, the RV sequence may be pre-determined.In another example, in case of accumulated TPC, the TPC command can beapplied only once on reception of the second stage SCI. The TPC commandmay not be re-applied, such as the TPC loop may not be updated with thevalue of the TPC command, when the second stage SCI is not present. Inanother example, in case of absolute TPC, the TPC command from thepreviously received second stage SCI can be applied to the datatransmission even when the second stage SCI is not present for thecurrent transmission. Similarly, the S-CSI request can only beconsidered to be triggered when the second stage SCI is received, andconsidered not triggered when the when the second stage SCI is notpresent.

In GC transmission, such as group communication, for NR V2x, there canbe two methods of group formation. In one method a group can be formedsemi statically by the V2x application layer where the group ID iscommunicated to the Radio Access Network (RAN). In another method groupcan be dynamically created with input parameters, such as communicationrange.

In cases where a UE can join a group at any time it may happen that a UEcannot obtain the second stage SCI when it joins the group. The UE maynot decode the PSSCH until it receives and correctly decodes the secondstage SCI and the procedure can be same as explained in previousembodiments. If the new UE is a new part of the group, then it canignore the occupied PSSCH resources for resource selection and it canignore decoding the PSSCH.

FIG. 10 is an example signal flow diagram 1000 of a UE joining a groupusing GC transmission according to a possible embodiment. The group caninclude a transmitting first UE 1010 and multiple receiving UEsincluding a second UE 1012, a third UE 1014, and a new fourth UE 1016.At 1020, in a first transmission process, the UE 1010 can GC communicatethe first stage SCI including the T/F of PDSSCH, NDI, destination groupID, the T/F of the second stage SCI, an indicator that indicates thepresence or absence of the second stage, and/or other information. At1025, the UE 1010 can transmit the second stage SCI including the RV,the HARQ process number, the MCS, the TPC command, the S-CSI request,and other information. At 1030, the UE 1010 can transmit UC data to theUE 1014. At 1035, in a second transmission process, the UE 1010 can GCcommunicate the first stage SCI including the T/F of PDSSCH, NDI,destination group ID, the T/F of the second stage SCI, an indicator thatindicates the presence or absence of the second stage, and/or otherinformation. At 1040, the UE 1010 can transmit UC data to the UE 1014.At 1045, in an n^(th) transmission process, the UE 1010 can GCcommunicate the first stage SCI including the T/F of PDSSCH, NDI,destination group ID, the T/F of the second stage SCI, an indicator thatindicates the presence or absence of the second stage, and/or otherinformation. At 1050, the UE 1016 can join the group by decoding thefirst stage SCI and destination group ID. If the first stage SCI messageis relevant to the UE 1016, then at 1055, the UE 1016 can send a GC orUC SFCI/PSFCH including an explicit indication to request transmissionof the second stage SCI.

For example, the new UE 1016 can decode the first stage SCI as part ofthe sensing procedure at every possible time slot. From the configuredLayer 2 destination ID or Layer 2 destination group ID/Layer 1destination group ID, the new UE 1016 can know whether it is part of thegroup and whether it should decode group cast transmission of PSSCH. Ifthe new UE 1016 needs to decode the PSSCH transmission, then the new UE1016 can transmit a GC transmission to the destination group ID toannounce its presence in the group with its own source ID/UE ID.Alternately, if the new UE 1016 knows the source ID of the transmittingUE 1010 from the first stage, then it can request the transmission ofsecond stage SCI.

FIG. 11 is an example illustration 1100 of a new UE announcing itself toa group according to a possible embodiment. The illustration 1100 canshow communication between a first UE 1110 and a second UE 1120. The UE1120 can be new to a group. At 1130, the new UE 1120 can send anannouncement indicating that it is present. The announcement can includean identifier of the new UE 1120. For example, the new UE 1120 canannounce itself to the group with its identifier, which can be a SCItransmission or any other physical layer discovery mechanism. At 1140,the UE 1110 can transmit the second stage SCI to the new UE 1120.

FIG. 12 is an example illustration 1200 of discovery and second stageSCI transmission for a group according to a possible embodiment. Theillustration 1200 can show communication between a first UE 1210 and asecond UE 1220. At 1230, the UE 1210 can send an inquiry about whatother UEs are available. At 1240, the UE 1220 can indicate that it ispresent and can send its UE identifier. At 1240, the UE 1210 cantransmit the second stage SCI. For example, for GC transmission, thesecond stage SCI can be transmitted to the newly joined UE 1220 in thegroup after the discovery procedure.

FIG. 13 is an example illustration 1300 of group specific signalingaccording to a possible embodiment. The illustration 1300 can showcommunication between a first UE 1310 and a second UE 1320 that is newto a group. At 1330, the UE 1310 can send an inquiry about what otherUEs are available. At 1340, the UE 1320 can indicate that it is presentand send its UE identifier. At 1350, the UE 1310 can send group specificsignaling including a CORESET of the second stage SCI, modificationperiodicity, a group internal identifier, and other information. Forexample, the group specific signaling can be transmitted to the newlyjoined UE 1320 after a discovery procedure. The group specific signalingcan contain details about the CORESET configuration of the second stageSCI for the UEs part of the group, can contain modification periodicity,and can contain other information.

The modification timer can be (re)started again in any of the previousembodiments when the transmitting UE schedules the second stage SCIbefore its expiry.

FIG. 14 is an example flowchart 1400 outlining the operation of awireless communication device, such as the UE 110, according to apossible embodiment. At 1410, first stage SCI can be determined. Thefirst stage SCI can include information indicating whether or not asecond stage SCI is being transmitted. The information in the firststage SCI can also include a presence indicator bit that indicateswhether or not the second stage SCI is being transmitted and/or whetheror not the second stage SCI should be decoded by at least one receivingUE. The information in the first stage SCI can also include an invalidresource assignment. The invalid resource assignment can indicate thesecond stage SCI is not being transmitted. For example, an invalid RBassignment for a second stage control channel resource can imply theabsence of second stage SCI transmission. As a further example, aninvalid value of at least one field in the first stage SCI field canindicate the absence of second stage SCI. The information in the firststage SCI can also indicate the periodicity of the second stage SCI.

At 1420, the first stage SCI can be periodically transmitted.Periodically transmitting the first stage SCI can include transmittingthe first stage SCI in every sidelink time slot including a scheduledsidelink data packet in a PSSCH. For example, first stage SCI can befrequent, which can imply that these parameters can be transmitted inall time slots along with every scheduled sidelink data packet in PSSCH,such as the minimum parameter set of the SCI that can be signaled eachtime a PSSCH is scheduled.

At 1430, the second stage SCI can be determined. The second stage SCIcan contain parameters for decoding data of a PSSCH. For example, thePSSCH decoding parameters can include MCS, TPC command, S-CSI request,CBG transmission information, CBG flushing information, DMRS SequenceInitialization, Source ID, beam/TCI state, spatial relation for S-CSI,and other information.

At 1440, the second stage SCI can be transmitted. The second stage SCIcan be transmitted less often than the first stage SCI.

According to a possible embodiment, a NACK can be received in a sidelinkfeedback channel when a receiving device does not decode the secondstage SCI. For example, if a receiving UE receives the first stage SCI,but determines that it did not decode the second stage SCI, thereceiving UE can transmit a NACK. As a further example, the NACK can betransmitted when the first stage SCI indicates the presence of secondstage SCI but the receiving UE fails to decode the second stage SCI.

According to another possible embodiment second stage SCI time-frequencyresources can be reused for data transmission when the second stage SCIis not being transmitted on the second stage SCI time-frequencyresources.

According to another possible embodiment, the second stage SCI can be afirst second stage SCI. A request to transmit updated schedulinginformation can be received. Updated scheduling information can betransmitted in a second second stage SCI in response to receiving therequest to transmit updated scheduling information.

According to another possible embodiment, the first stage SCI caninclude a modification period of the second stage SCI. Data can betransmitted on a PSSCH based on the second stage SCI until themodification period expires.

According to another possible embodiment, periodically transmitting thefirst stage SCI can include groupcasting the first stage SCI to a groupof UEs. A communication can be received from a UE that is new to thegroup of UEs after transmitting the second stage SCI. The second stageSCI can be retransmitted in response to receiving the communication.

According to another possible embodiment, a determination can be made asto whether to transmit two-stage sidelink control information. The firststage sidelink control information can be determined in response todetermining to transmit two-stage sidelink control information. Also,the second stage sidelink control information can be determined inresponse to determining to transmit two-stage sidelink controlinformation.

FIG. 15 is an example flowchart outlining operation of a wirelesscommunication device, such as the UE 110, according to a possibleembodiment. At 1510, first stage SCI can be periodically received. Thefirst stage SCI can include information indicating whether or not asecond stage SCI is being transmitted. The information of the firststage SCI can also indicate when the second stage SCI is beingtransmitted. At 1520, the second stage SCI can be received based on theinformation indicating whether or not the second stage SCI is beingtransmitted. At 1530, a PSSCH can be decoded based on the first stageSCI and the second stage SCI. According to possible embodiments, otherdisclosed reciprocal operations can be performed for responding to atransmitting UE's sidelink transmissions.

It should be understood that, notwithstanding the particular steps asshown in the figures, a variety of additional or different steps can beperformed depending upon the embodiment, and one or more of theparticular steps can be rearranged, repeated or eliminated entirelydepending upon the embodiment. Also, some of the steps performed can berepeated on an ongoing or continuous basis simultaneously while othersteps are performed. Furthermore, different steps can be performed bydifferent elements or in a single element of the disclosed embodiments.

FIG. 16 is an example block diagram of an apparatus 1600, such as the UE110, the network entity 120, or any other wireless communication devicedisclosed herein, according to a possible embodiment. The apparatus 1600can include a housing 1610, a controller 1620 coupled to the housing1610, audio input and output circuitry 1630 coupled to the controller1620, a display 1640 coupled to the controller 1620, a memory 1650coupled to the controller 1620, a user interface 1660 coupled to thecontroller 1620, a transceiver 1670 coupled to the controller 1620, atleast one antenna 1675 coupled to the transceiver 1670, and a networkinterface 1680 coupled to the controller 1620. The apparatus 1600 maynot necessarily include all of the illustrated elements for differentembodiments of the present disclosure. The apparatus 1600 can performthe methods described in all the embodiments.

The display 1640 can be a viewfinder, a Liquid Crystal Display (LCD), aLight Emitting Diode (LED) display, an Organic Light Emitting Diode(OLED) display, a plasma display, a projection display, a touch screen,or any other device that displays information. The transceiver 1670 canbe one or more transceivers that can include a transmitter and/or areceiver. The audio input and output circuitry 1630 can include amicrophone, a speaker, a transducer, or any other audio input and outputcircuitry. The user interface 1660 can include a keypad, a keyboard,buttons, a touch pad, a joystick, a touch screen display, anotheradditional display, or any other device useful for providing aninterface between a user and an electronic device. The network interface1680 can be a Universal Serial Bus (USB) port, an Ethernet port, aninfrared transmitter/receiver, an IEEE 1394 port, a wirelesstransceiver, a WLAN transceiver, or any other interface that can connectan apparatus to a network, device, and/or computer and that can transmitand receive data communication signals. The memory 1650 can include aRandom-Access Memory (RAM), a Read Only Memory (ROM), an optical memory,a solid-state memory, a flash memory, a removable memory, a hard drive,a cache, or any other memory that can be coupled to an apparatus.

The apparatus 1600 or the controller 1620 may implement any operatingsystem, such as Microsoft Windows®, UNIX®, LINUX®, Android™, or anyother operating system. Apparatus operation software may be written inany programming language, such as C, C++, Java, or Visual Basic, forexample. Apparatus software may also run on an application framework,such as, for example, a Java® framework, a .NET® framework, or any otherapplication framework. The software and/or the operating system may bestored in the memory 1650, elsewhere on the apparatus 1600, in cloudstorage, and/or anywhere else that can store software and/or anoperating system. The apparatus 1600 or the controller 1620 may also usehardware to implement disclosed operations. For example, the controller1620 may be any programmable processor. Furthermore, the controller 1620may perform some or all of the disclosed operations. For example, atleast some operations can be performed using cloud computing and thecontroller 1620 may perform other operations. At least some operationscan also be performed computer executable instructions executed by atleast one computer processor. Disclosed embodiments may also beimplemented on a general-purpose or a special purpose computer, aprogrammed microprocessor or microprocessor, peripheral integratedcircuit elements, an application-specific integrated circuit or otherintegrated circuits, hardware/electronic logic circuits, such as adiscrete element circuit, a programmable logic device, such as aprogrammable logic array, field programmable gate-array, or the like. Ingeneral, the controller 1620 may be any controller or processor deviceor devices capable of operating an apparatus and implementing thedisclosed embodiments. Some or all of the additional elements of theapparatus 1600 can also perform some or all of the operations of thedisclosed embodiments.

In operation, the apparatus 1600 can perform the methods and operationsof the disclosed embodiments. The transceiver 1670 can transmit andreceive signals, including data signals and control signals that caninclude respective data and control information. The controller 1620 cangenerate and process the transmitted and received signals andinformation.

According to a possible embodiment, the controller 1620 can determinefirst stage SCI. The first stage SCI can include information indicatingwhether or not a second stage SCI is being transmitted. The informationin the first stage SCI can indicate the periodicity of the second stageSCI. The information in the first stage SCI can also include a presenceindicator bit that indicates whether or not the second stage SCI isbeing transmitted and/or whether or not the second stage SCI should bedecoded by at least one receiving UE. The information in the first stageSCI can also include an invalid resource assignment. The invalidresource assignment can indicate the second stage SCI is not beingtransmitted. The transceiver 1670 can periodically transmit the firststage SCI. The controller 1620 can determine the second stage SCI. Thetransceiver 1670 can transmit the second stage SCI. The second stage SCIcan be transmitted less often than the first stage SCI.

According to a possible embodiment, the transceiver 1670 can receive aNACK in a sidelink feedback channel when a receiving device does notdecode the second stage SCI.

According to a possible embodiment, the controller 1620 can reusetime-frequency resources allocated for second stage SCI for datatransmission when the second stage SCI is not being transmitted on thesecond stage SCI time-frequency resources.

According to a possible embodiment, the second stage SCI can be a firstsecond stage SCI. The transceiver 1670 can receive a request to transmitupdated scheduling information. The transceiver 1670 can transmitupdated scheduling information in a second second stage SCI in responseto receiving the request to transmit updated scheduling information.

According to a possible embodiment, the first stage SCI can include amodification period of the second stage SCI. The transceiver 1670 cantransmit data on a PSSCH based on the second stage SCI until themodification period expires.

According to a possible embodiment, the transceiver 1670 canperiodically transmit the first stage SCI by groupcasting the firststage SCI to a group of UEs. The transceiver 1670 can receive acommunication from a UE that is new to the group of UEs aftertransmitting the second stage SCI. The transceiver 1670 can retransmitthe second stage SCI in response to receiving the communication.

At least some embodiments can provide for optimization of two stage SCIwhere the first stage of the SCI can contain sensing related resourcereservation information that aid anonymous UEs to find empty resourcesplus a fast-varying part of the SCI because first stage may need to betransmitted all the time. The second stage SCI can contain a slowvarying part of the SCI, which need not be transmitted in all timeslots.

An indication can be provided in the first stage that indicates when thesecond stage SCI will be transmitted. The indication can includemodification periodicity, at least one bit, 0/1, to indicate thepresence or absence of second stage, an implicit indication based on theinvalid/valid RB assignment for the second stage SCI, and/or can includeother information. When the second stage SCI is not being transmitted,then a receiving UE can assume the second stage SCI content as same asbefore. As a UE procedure when the UE does not decode the second stageSCI, the UE may not attempt to decode the transport block of PSSCH.

For UE behavior for GC communication, a UE can decode the first stageSCI as part of the sensing procedure at every possible time slot. Fromthe destination ID/destination group ID, the UE can know whether itcan/needs to decode PSSCH. If the UE can/needs to decode PSSCHtransmission, then the UE can transmit either a UC SCI/SFCI to thetransmitting UE, if the source ID is known from the first stage SCI orthe UE can GC/BC to the destination group ID requesting the second stageSCI transmission. Otherwise, the UE can mark the used PSSCH resourcesfor resource selection and can ignore decoding the PSSCH.

According to possible embodiments, fast varying first stage SCI can beconfigured/determined. The fast varying first stage SCI can containsensing related resource reservation information that can aid theanonymous UEs in finding empty resources, by indicating what resourcesare being used by the transmitting UE, plus the first stage SCI. Thefirst stage SCI can be continuously transmitted. A slow-varying secondstage SCI can be configured/determined. The second stage SCI need not betransmitted in all time slots. The second stage SCI can be transmitted.The second stage SCI is transmitted less often than the first stage SCI.

The first stage SCI can include an indication that indicates when thesecond stage SCI will be transmitted, modification periodicity, a bitthat indicates the presence or absence of second stage, and/or animplicit indication based on an invalid/valid RB assignment for thesecond stage SCI. For example, a modification period can be a periodduring which changes to a control channel, such as a multipoint controlchannel, can be indicated/notified.

The first stage SCI can include information including resourceallocation of a second control channel for the second stage SCI,transmission periodicity of the second stage SCI, second stage SCIformat, second stage SCI sizes, and/or second stage SCI aggregationlevel.

Second stage content from a previously transmitted second stage SCI canbe used as a current SCI if the second stage SCI is not beingsubsequently transmitted.

According to possible embodiments, fast varying first stage SCI can bereceived. The fast varying first stage SCI can contain sensing relatedresource reservation information that aids anonymous UEs to find emptyresources, can contain the first stage SCI, and can contain second stageSCI. The first stage SCI can be continuously received. Slow varyingsecond stage SCI can be received. The slow varying second stage SCI neednot be transmitted in all time slots. The second stage SCI can bereceived less often than the first stage SCI.

The first stage SCI can include an indication that indicates when thesecond stage SCI will be transmitted, modification periodicity, a bitthat indicates the presence or absence of second stage, and/or animplicit indication based on an invalid/valid RB assignment for thesecond stage SCI.

Second stage SCI content can be assumed to be the same as a previoussecond stage SCI if a later second stage SCI is not received. Forexample, a receiving UE can determine the second stage SCI content assame as before.

A TB of a PSSCH can be abstained from being decoded if the first stageSCI does not indicate second stage SCI is being transmitted, indicatesthe second stage SCI is not being transmitted, and/or a modificationperiod timer has not expired. For example, a receiving UE may notmonitor, such as attempt to decode, the TB of the PSSCH. The first stageSCI can be decoded as part of a sensing procedure at every possible timeslot and from the destination ID/destination group ID. A determinationcan be made as to whether a PSSCH needs to be decoded

If the PSSCH needs to be decoded, a UC SCI/SFCI can be transmitted to aUE that transmitted the first stage SCI, if the source identifier isknown from the first stage SCI. Alternately, a GC/BC transmission can besent to the destination group identifier requesting the Second stage SCItransmission.

Used PSSCH resources can be marked for resource selection. DecodingPSSCH can be ignored if the PSSCH does not need to be decoded.

At least some methods of this disclosure can be implemented on aprogrammed processor. However, the controllers, flowcharts, and modulesmay also be implemented on a general purpose or special purposecomputer, a programmed microprocessor or microcontroller and peripheralintegrated circuit elements, an integrated circuit, a hardwareelectronic or logic circuit such as a discrete element circuit, aprogrammable logic device, or the like. In general, any device on whichresides a finite state machine capable of implementing the flowchartsshown in the figures may be used to implement the processor functions ofthis disclosure.

At least some embodiments can improve operation of the discloseddevices. Also, while this disclosure has been described with specificembodiments thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart. For example, various components of the embodiments may beinterchanged, added, or substituted in the other embodiments. Also, allof the elements of each figure are not necessary for operation of thedisclosed embodiments. For example, one of ordinary skill in the art ofthe disclosed embodiments would be enabled to make and use the teachingsof the disclosure by simply employing the elements of the independentclaims. Accordingly, embodiments of the disclosure as set forth hereinare intended to be illustrative, not limiting. Various changes may bemade without departing from the spirit and scope of the disclosure.

In this document, relational terms such as “first,” “second,” and thelike may be used solely to distinguish one entity or action from anotherentity or action without necessarily requiring or implying any actualsuch relationship or order between such entities or actions. The phrase“at least one of,” “at least one selected from the group of,” or “atleast one selected from” followed by a list is defined to mean one,some, or all, but not necessarily all of, the elements in the list. Theterms “comprises,” “comprising,” “including,” or any other variationthereof, are intended to cover a non-exclusive inclusion, such that aprocess, method, article, or apparatus that comprises a list of elementsdoes not include only those elements but may include other elements notexpressly listed or inherent to such process, method, article, orapparatus. An element proceeded by “a,” “an,” or the like does not,without more constraints, preclude the existence of additional identicalelements in the process, method, article, or apparatus that comprisesthe element. Also, the term “another” is defined as at least a second ormore. The terms “including,” “having,” and the like, as used herein, aredefined as “comprising.” Furthermore, the background section is writtenas the inventor's own understanding of the context of some embodimentsat the time of filing and includes the inventor's own recognition of anyproblems with existing technologies and/or problems experienced in theinventor's own work.

We claim:
 1. A method comprising: determining, at a user equipment,first stage sidelink control information, the first stage sidelinkcontrol information including information indicating whether or not asecond stage sidelink control information is being transmitted;periodically transmitting, by the user equipment, the first stagesidelink control information; determining the second stage sidelinkcontrol information; and transmitting the second stage sidelink controlinformation.
 2. The method according to claim 1, wherein the informationin the first stage sidelink control information indicates theperiodicity of the second stage sidelink control information.
 3. Themethod according to claim 1, wherein the second stage sidelink controlinformation is transmitted less often than the first stage sidelinkcontrol information.
 4. The method according to claim 1, wherein theinformation in the first stage sidelink control information comprises apresence indicator bit that indicates at least one selected from whetheror not the second stage sidelink control information is beingtransmitted and whether or not the second stage sidelink controlinformation should be decoded by at least one receiving user equipment.5. The method according to claim 1, wherein the information in the firststage sidelink control information comprises an invalid resourceassignment, where the invalid resource assignment indicates the secondstage sidelink control information is not being transmitted.
 6. Themethod according to claim 1, further comprising receiving a negativeacknowledgement in a sidelink feedback channel when a receiving devicedoes not decode the second stage sidelink control information.
 7. Themethod according to claim 1, further comprising reusing second stagesidelink control information time-frequency resources for datatransmission when the second stage sidelink control information is notbeing transmitted on the second stage sidelink control informationtime-frequency resources.
 8. The method according to claim 1, whereinthe second stage sidelink control information comprises first secondstage sidelink control information, wherein the method furthercomprises: receiving a request to transmit updated schedulinginformation; and transmitting updated scheduling information in a secondsecond stage sidelink control information in response to receiving therequest to transmit updated scheduling information.
 9. The methodaccording to claim 1, wherein the first stage sidelink controlinformation includes a modification period of the second stage sidelinkcontrol information, and wherein the method further comprisestransmitting data on a physical sidelink shared channel based on thesecond stage sidelink control information until the modification periodexpires.
 10. The method according to claim 1, wherein periodicallytransmitting the first stage sidelink control information comprisesgroupcasting the first stage sidelink control information to a group ofuser equipments, wherein the method further comprises: receiving acommunication from a user equipment that is new to the group of userequipments after transmitting the second stage sidelink controlinformation; and retransmitting the second stage sidelink controlinformation in response to receiving the communication.
 11. The methodaccording to claim 1, wherein the second stage sidelink controlinformation is transmitted on at least one selected from a physicalsidelink shared channel resource and a physical sidelink control channelresource.
 12. The method according to claim 1, further comprisingdetermining whether to transmit two-stage sidelink control information,wherein the first stage sidelink control information is determined inresponse to determining to transmit two-stage sidelink controlinformation, and wherein the second stage sidelink control informationis determined in response to determining to transmit two-stage sidelinkcontrol information.
 13. An apparatus comprising: a controller thatdetermines first stage sidelink control information, the first stagesidelink control information including information indicating whether ornot a second stage sidelink control information is being transmitted,and determines the second stage sidelink control information; and atransceiver that periodically transmits the first stage sidelink controlinformation, and transmits the second stage sidelink controlinformation.
 14. The apparatus according to claim 13, wherein theinformation in the first stage sidelink control information indicatesthe periodicity of the second stage sidelink control information. 15.The apparatus according to claim 13, wherein the information in thefirst stage sidelink control information comprises a presence indicatorbit that indicates at least one selected from whether or not the secondstage sidelink control information is being transmitted and whether ornot the second stage sidelink control information should be decoded byat least one receiving user equipment.
 16. The apparatus according toclaim 13, wherein the information in the first stage sidelink controlinformation comprises an invalid resource assignment, where the invalidresource assignment indicates the second stage sidelink controlinformation is not being transmitted.
 17. The apparatus according toclaim 13, wherein the controller reuses time-frequency resourcesallocated for second stage sidelink control information for datatransmission when the second stage sidelink control information is notbeing transmitted on the second stage sidelink control informationtime-frequency resources.
 18. The apparatus according to claim 13,wherein the second stage sidelink control information comprises firstsecond stage sidelink control information, wherein the transceiverreceives a request to transmit updated scheduling information; andtransmits updated scheduling information in a second second stagesidelink control information in response to receiving the request totransmit updated scheduling information.
 19. The apparatus according toclaim 13, wherein the first stage sidelink control information includesa modification period of the second stage sidelink control information,and wherein transceiver transmits data on a physical sidelink sharedchannel based on the second stage sidelink control information until themodification period expires.
 20. The apparatus according to claim 13,wherein the transceiver periodically transmits the first stage sidelinkcontrol information by groupcasting the first stage sidelink controlinformation to a group of user equipments, receives a communication froma user equipment that is new to the group of user equipments aftertransmitting the second stage sidelink control information, andretransmits the second stage sidelink control information in response toreceiving the communication.